CHICAGO, IL - SEPTEMBER 20: Team Europe Novak Djokovic of Serbia talks with Team Europe Roger Federer of Switzerland during practice prior to the Laver Cup at the United Center on September 20, 2018 in Chicago, Illinois. The Laver Cup consists of six players from Team World competing against their counterparts from Team Europe. John McEnroe will captain Team World and Team Europe will be captaine

The Australian legend, who claimed 11 grand slam crowns in his career through the 1960s and 70s, was asked who would win in a fifth set thriller at Wimbledon.

He wasn't too keen on comparing eras.

I had a little wooden racket and Federer plays with large-headed racket," the 80-year-old grass court master replied on Twitter. "That's a huge difference. You're limited with what you can do with a smaller racket. It's almost an impossible question to answer because of the technology."

It comes as Federer prepares to team up with long-time Open rival Novak Djokovic at this year's Laver Cup in Chicago.

Federer and Djokovic have played against each other 46 times. From Monaco to Shanghai and everywhere in between. Regular, run-of- the-mill tournaments and major finals.

On Friday night, they play on the same side of the net for the first time. Federer and Djokovic will close out the first day of the second edition of the Laver Cup when they take on Jack Sock and Kevin Anderson in doubles at the United Center. Federer and Djokovic are playing for Team Europe, while Sock and Anderson are competing for Team World in the Ryder Cup-style event.

This should be good.

Rod Laver doesn’t want to compare eras.

"We have had so many great battles in all the singles courts, and to finally team up together I think is going to be very special for both of us," Federer said Thursday. "I think we still have to talk over it a little bit exactly maybe either who's going to take the lead or, you know, how do we play exactly." The pairing of Federer and Djokovic adds a little spice to an event long on star power and light on any real stakes. While world No. 1 Rafael Nadal and No. 4 Juan Martin del Potro are out with injuries, the Laver Cup has seven of the top 11 players in the ranking and 10 of the top 20.

But it arrives at the home of the NBA's Bulls and NHL's Blackhawks just a couple weeks after Djokovic beat del Potro in the US Open final for his 14th Grand Slam title. There are no majors left this year and the next big tournament isn't until next month in Shanghai.

While the event looks and feels like a glorified exhibition - check out the unusual black court and the celebrations for the youthful Team World whenever it wins a big point - John Isner brusquely swatted away a question about the level of competition.

"Honestly, that question really annoys me," the 6-foot-10 American said. "One- hundred per cent serious. This is not an exhibition at all. At all." Federer and his management team played a key role in the creation of the event, and the Swiss star helped lead Team Europe to the victory last year in Prague. The inaugural edition also was marked by a splashy doubles pairing involving Federer, who teamed with Nadal for the first time for a 6-4, 1-6, 10-5 victory over Sock and fellow American Sam Querrey.

Asked about the matchup with Federer and Djokovic, Sock cracked: "Who's that?" "Yeah, obviously going to be a legendary team," he continued "We got a little bit of it last year." Djokovic and Federer last played against each other in the Cincinnati final on Aug. 19, when Djokovic won 6-4, 6-4 to become the player to claim all nine ATP Masters 1000 events since the series started in 1990. Djokovic leads the all- time series with 24 victories.

"This is what this competition is all about, you know, bringing us all together," Djokovic said.

How Djokovic and Federer do together remains to be seen. Sock is one of the world's top doubles players, and the 32-year-old Anderson, who is from South Africa and played in college at the University of Illinois, is having a terrific year.

But the possibilities for the talented pairing sure looked pretty good. "I think I will take the deuce side. If Novak is OK with that, I will be happy to play on the deuce side," Federer said when asked where each player might set up.